Serum or plasma for use in clinical chemistry analysis is usually prepared by drawing whole blood from a patient into vacuumed tubes. The liquid is permitted to stand for a period of time to allow a clot to form. The sample is next centrifuged to separate the liquid from the solid particles. The serum or plasma is thereafter transferred into another container.
It is essential to obtain fibrin-free serum without unnecessary delay in that certain serum constituents may be changed by hemolysis, delayed separation and other factors.
Serum separating procedures utilized in the laboratory is a primary source of frequent contact of personnel to infectious diseases by either direct contact with the serum and/or by aerosol eminating from uncapped tubes while they are spinning.
Many devices and apparatus have been developed to improve and aid the serum separation. These include conventional squeezing method, barrier formation using beads, semi-permeable disks and semi-solid polymer, transfer of serum into a plastic container by passage through a hole or tube in a rubber or flexible plastic disk, and finally to the sealed container of polymer that is placed on the top of the blood-collecting tube just before centrifugation. The semi-solid polymer falls from the container through the serum and forms a barrier between the serum and the clot. More recent devices also include the vacuum tube having the polymer within the tubes, wherein the polymer falls and forms a barrier between the two phases during centrifugation. These devices aid the separation of the serum but not the transfer of the serum or plasma into other containers.
Although it is the primary purpose of the prior art devices to obtain fibrin-free sample, it has been found that small particles of the polymer floating on the surface of the serum may cause even a more serious clogging problem than fibrin for the automated instrument.